Surgical Robot Arm Force Calibration for Accurate End-Effector Spread
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing surgical robot arm control systems fail to accurately reflect the surgeon's intended movements due to inaccuracies in predicting the spread angle between end effector elements, leading to issues like over-closed configurations and perceptible errors.
Innovation Solution
A control system that adjusts instrument drive forces and predicts a spread offset value using kinematic equations, compensating for lost motion and manufacturing variability to ensure the robotic surgical instrument aligns with the surgeon's inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the surgical robot arm uses standard kinematic control without compensation, then the control system is simple, but the spread angle prediction accuracy deteriorates due to lost motion and manufacturing variability
Solution Approach 1:
The control system performs preliminary calibration by applying multiple instrument drive forces to the robotic surgical instrument and measuring the actual spread angles. This preliminary action establishes a calibration dataset that compensates for lost motion and manufacturing variability before actual surgical operations, thereby improving spread angle prediction accuracy without adding complexity to the real-time control system.
Solution Approach 2:
The system implements feedback by comparing predicted spread angles (from kinematic equations) with actual measured spread angles during calibration. This feedback loop allows the system to determine optimal instrument drive forces and store calibration data that corrects for systematic errors, resolving the contradiction between simple control and accurate prediction.
2Measurement precision
If the system applies high instrument drive forces to overcome lost motion, then the spread angle accuracy improves, but the risk of over-closed configurations increases
Solution Approach 1:
The calibration process applies instrument drive forces that exceed normal operating ranges to fully overcome lost motion and establish accurate correspondence between drive forces and spread angles. By performing this excessive action during calibration rather than during surgery, the system achieves high accuracy while maintaining safety during actual operations through the stored calibration data.
Solution Approach 2:
The system cushions against the risk of over-closed configurations by performing preliminary calibration that maps the full range of instrument drive forces to actual spread angles. This beforehand preparation creates a safety buffer by identifying the precise relationship between drive forces and configurations, preventing excessive forces from causing harmful over-closed states during surgery.
3Manufacturing precision
If the control system performs comprehensive calibration with multiple drive forces, then the instrument alignment accuracy improves, but the calibration time increases
Solution Approach 1:
The system performs comprehensive calibration as a preliminary action before surgical procedures. By completing the time-consuming calibration process in advance, the system establishes accurate instrument alignment data without delaying actual surgical operations, thus resolving the contradiction between accuracy and time loss during surgery.
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A control system for controlling a surgical robot arm, the surgical robot arm having a drive mechanism configured for driving a robotic surgical instrument, said robotic surgical instrument comprising a first end effector element and a second end effector element, the drive mechanism comprising one or more interface elements configured to interface with the robotic surgical instrument for controlling a spread angle between the first end effector element and the second end effector element, the control system being configured to: cause an instrument drive force applied at the one or more interface elements to be varied; measure, at each of a plurality of times, the instrument drive force applied at the one or more interface elements; determine, for each of the plurality of times, a force behaviour value using a derivative of the measured instrument drive force with respect to the time at that time; determine an offset value in dependence on the plurality of determined force behaviour values; and control, in dependence on the offset value, the surgical robot arm to control the spread angle between the first end effector element and the second end effector element of the robotic surgical instrument.